The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Plasma arc torches, also known as electric arc torches, are commonly used for cutting, marking, gouging, and welding metal workpieces by directing a high energy plasma stream consisting of ionized gas particles toward the workpiece. In a typical plasma arc torch, the gas to be ionized is supplied to a distal end of the torch and flows past an electrode before exiting through an orifice in the tip, or nozzle, of the plasma arc torch. The electrode has a relatively negative potential and operates as a cathode. Conversely, the torch tip constitutes a relatively positive potential and operates as an anode during piloting. Further, the electrode is in a spaced relationship with the tip, thereby creating a gap, at the distal end of the torch. In operation, a pilot arc is created in the gap between the electrode and the tip, often referred to as the plasma arc chamber, wherein the pilot arc heats and subsequently ionizes the gas. The ionized gas is blown out of the torch and appears as a plasma stream that extends distally off the tip. As the distal end of the torch is moved to a position close to the workpiece, the arc jumps or transfers from the torch tip to the workpiece with the aid of a switching circuit activated by the power supply. Accordingly, the workpiece serves as the anode, and the plasma arc torch is operated in a “transferred arc” mode.
In many plasma arc torches, secondary gas flow is used to control cut quality of the main plasma stream and to provide cooling to consumable components of the plasma arc torch. Generally, two (2) primary methods of introducing the secondary gas have been used in the art. In the first method, secondary gas is directed towards and impinges directly upon the plasma stream. Such a method is used primarily in automated plasma arc torches having relatively high cutting precision, as compared with manual methods. In the second method, the secondary gas is introduced coaxially with the plasma stream such that a curtain of secondary gas is formed around the plasma stream, which does not directly impinge upon the plasma stream.
Improved methods of introducing the secondary gas are continuously desired in the field of plasma arc cutting in order to improve both cut quality and cutting performance of the plasma arc torch.